Learn Portuguese (Portugal): O inimigo vigia-o como se soubesse a identidade dele. - The enemy watches him as if they knew his identity.

The phrase como se (as if) always triggers the Imperfect Subjunctive tense in Portuguese. It introduces a hypothetical situation: the enemy doesn't actually know his identity, but they are acting as if they did. Soubesse is the third-person singular form of saber in this tense.

The English translation says "they knew", so why isn't the verb plural (soubessem)?

In Portuguese, the subject is O inimigo (The enemy), which is grammatically singular, so the verb must match it with the singular soubesse. The English translation uses "they" as a singular gender-neutral pronoun, but Portuguese grammar strictly follows the noun's number.

Can you explain the hyphen in vigia-o?

The -o is a direct object pronoun meaning "him". In European Portuguese affirmative main clauses, these pronouns are attached to the end of the conjugated verb with a hyphen. Vigia means "watches", so vigia-o directly translates to "watches him".

Why use dele instead of the possessive sua for "his"?

Both a identidade dele and a sua identidade mean "his identity" and are correct. However, sua can mean "his", "hers", or "yours" (when speaking formally). Using dele (literally "of him") is very common because it completely removes any ambiguity.